Upper level ridging over much of the western United States led to deadly heat at the beginning of July. Temperatures at Phoenix Sky Harbor during this time peaked at 107 degrees, which is normal for this time of year.
Every event with a place to put it; 5 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS PSR wrote it up.
Upper level ridging over much of the western United States led to deadly heat at the beginning of July. Temperatures at Phoenix Sky Harbor during this time peaked at 107 degrees, which is normal for this time of year. However, low temperatures only cooled to around 90 degrees at times, providing little overnight relief. According to the Maricopa County Department of Public Health, 14 heat-associated fatalities occurred during this time.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Phoenix, AZ wrote its last area forecast discussion before the first event at Jul 1, 4:32 PM MST, 28 minutes earlier.
Area Forecast Discussion National Weather Service Phoenix AZ 432 PM MST Thu Jul 1 2021 .UPDATE...Updated Aviation Discussion. && .SYNOPSIS... Scattered showers and thunderstorms will be common over the higher terrain and more isolated on the lower elevations the rest of the week. Gusty winds with localized blowing dust, and localized heavy rain/flooding will be the main impacts. A slow decline in storm activity begins by early next week, but daily storm chances over the eastern Arizona high terrain should persist. Temperatures will be near normal the rest of this week before increasing slightly early next week. && .DISCUSSION... Convection today developed earlier than it did yesterday, by 9:30 AM across the northern AZ high terrain, White Mtns, and in southeast AZ. However, for the most part, storms have been less intense. More so, the coverage of strong/marginally severe storms have been less. One factor may be slightly lower CAPE values seen on 12Z morning soundings and RAP mesoanalysis. Steering flow is still very week with 850-300 mb mean winds analyzed around 5-10 kts, so storms have been nearly stationary. PWAT values have fallen slightly, but mixing ratios remain near 10-11 g/kg, so storms have still been efficient rain producers with rain rates upwards of 0.5-1.0"/hr. Flooding impacts over very localized terrain areas will be possible with any storms that experience an extended resonance times over one area before dissipating. DCAPE is also notably lower today across southeast AZ, so the chance for strong downburst/outflow winds is lower today in Gila and Pinal county. HREF probability of >35 mph winds is around 20-30% chance. Wind impacts and blowing dust potential will be slightly higher out in the Kofas area of Yuma and La Paz counties, where DCAPE values are higher. While convection should dissipate after sunset, a weak inverted trough moving northwest out of Sonora Friday morning may generate isolated to scattered ACCAS showers. Most CAMs favor progression of the wave, and best shower chances, through portions of southwest AZ and southeast CA, but coverage could extend up into south-central AZ. Forecast soundings in the Yuma area Friday morning support embedded thunder chances as well, with minimal elevated CAPE. Any stronger shower could produce gusty downburst winds. .PREVIOUS DISCUSSION... For Friday, there are signs of a decent moisture push out of northern Mexico early in the morning with some potential shower activity moving into southwest and portions of south-central AZ. This may be partially due to the inverted trough slowly moving westward along the border, but also possibly a reflection of the increasing broad southeasterly flow ramping up across the region as the upper level high center shifts into the Four Corners area. Low level mixing ratios do not really increase all that much on Friday, but the higher values do spread westward to the Lower CO River Valley. The HREF does show a slight increase in storm activity for Friday across southeast AZ and the high terrain east of Phoenix as well as overall MUCAPEs through south- central Arizona. The slight uptick in moisture and instability on Friday should result in a bit better chances of storms across the south- central AZ deserts, but weak winds aloft and a very weak southeasterly steering flow would likely again limit storm longevity. Storm chances will remain over the upcoming weekend with both days showing fairly plentiful moisture, possibly even too much moisture aloft resulting in possible issues with extensive cloudiness and the lack of instability. GEFS shows PWATs increasing to around 1.75" by Saturday morning, likely due to a deepening southeasterly fetch of moisture out of northern Mexico. Models show the upper level ridge is likely to remain parked over northern AZ over the weekend with very weak flow aloft across southern Arizona. This scenario could mean we will be quite active on one or both (unlikely) of the days, but it may also just result in modestly unstable, but fairly capped environment. Afternoon/evening storm chances will likely depend on the amount of leftover clouds from the previous night/morning and if there is any help from possible disturbances/inverted troughs. If there ends up being plentiful moisture, storm threats are likely to transition more toward heavy rainfall and localized flooding (as long as instability is present). After near normal temperatures through Friday, temperature guidance for Saturday and Sunday shows a much higher spread. Highs are still most likely to reach near normals over the weekend, but due to the higher potential for clouds and storms there is definitely more room for highs barely making it to 100 degrees in some areas. A subtle southward shift in the position of the upper level high center looks likely for early next week and this should result in diminishing moisture and lower storm chances by Monday or Tuesday. As of now, the first half of next week will favor storm chances over the eastern Arizona high terrain with limited chances over the lower deserts. Temperatures for the first half of next week are also likely to creep upward slightly with fairly high (40-60%) probabilities of the western deserts reaching 110 degrees again, while Phoenix's probability of reaching 110 degrees mostly stays below 30%. && .AVIATION...Updated at 2330Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Westerly to northwesterly winds will predominate across most of the TAF sites through this afternoon with speeds reaching 8-12 kts and occasionally gusting to 18-22 kts. There is less thunderstorm activity today compared to previous days, with diminishing chances for any storms within the terminal area (10-15%) through this evening. However, the few distant thunderstorms that are out there still have the potential for sending outflow winds that could cause abrupt wind changes. Right now, one boundary is being tracked east of KIWA but latest radar trends indicate this boundary weakening and unlikely to reach any of the terminals. Otherwise, a few periods of southerly to variable winds are possible tonight a few hours after sunset as the overnight easterly winds become predominate. For tomorrow, there is a low chance for isolated thunderstorms south of the Phoenix area early Friday morning, but current forecast does not have this impacting the Phoenix area. Winds will shift westerly again by the early afternoon as guidance trends indicate an uptick in thunderstorm development in the vicinity between 00/04z with the threat for multiple outflow boundaries and wind shifts. Southeast California/Southwest Arizona including KIPL and KBLH: There are no major aviation weather concerns as convection should remain east of KBLH and south of the US/MX border. Any outflow winds from these storms will likely reinforce the predominate winds. At KIPL, south-southeasterly winds will predominate through the forecast while southerly winds will remain at KBLH. && .FIRE WEATHER... Sunday through Thursday: High pressure is expected to become centered over Arizona over the weekend. A slow decline in atmospheric moisture is also anticipated to begin by early next week. Thus, the best potential for storms with locally heavy rain looks to be this weekend. Otherwise, a familiar Monsoon season pattern will be in place with storms primarily focused over the higher terrain producing outflows that spread to the lower deserts and in turn generate isolated new storms. Temperatures will start off near normals followed by slight warming early next week. Min RH values will generally be in the 20-30% range through Sunday before decreasing to 15-25% on Tuesday. Max RHs will be 40-60% for most areas through Monday morning before decreasing to 30-50% starting Tuesday. As the moisture decreases, temperatures will rise slightly, with highs around 110 degrees by early next week. Apart from thunderstorms, wind patterns will follow familiar diurnal patterns. && .SPOTTER INFORMATION STATEMENT... Spotters should follow standard reporting procedures. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && DISCUSSION...Benedict PREVIOUS DISCUSSION...Kuhlman AVIATION...AD FIRE WEATHER...Benedict/Kuhlman
Special Weather Statement National Weather Service Phoenix AZ 404 PM MST Thu Jul 1 2021 AZZ534-537-538-012330- Aguila Valley AZ-Tonopah Desert AZ-Northwest Valley AZ- 404 PM MST Thu Jul 1 2021 ...SIGNIFICANT WEATHER ADVISORY FOR MARICOPA COUNTY UNTIL 430 PM MST... At 403 PM MST, Doppler radar was tracking a strong thunderstorm 7 miles south of Wickenburg, moving southeast at 10 mph. Pea size hail and winds in excess of 40 mph will be possible with this storm. Locations impacted include... Morristown. This includes the following highways... US Highway 60 between mile markers 117 and 124. AZ Route 74 between mile markers 1 and 4. LAT...LON 3382 11288 3394 11281 3388 11255 3369 11266 TIME...MOT...LOC 2303Z 294DEG 9KT 3385 11278 LJH
The national radar mosaic for the moment the first event began.
5 heat. Local standard time, as filed.
Two fatalities (1 direct and 1 indirect) were reported by the Maricopa County Department of Public Health, with their details, such as age, gender, circumstances, and exact location unavailable.
Three indirect fatalities were reported by the Maricopa County Department of Public Health, with their details, such as age, gender, circumstances, and exact location unavailable.
Four fatalities (1 direct and 3 indirect) were reported by the Maricopa County Department of Public Health, with their details, such as age, gender, circumstances, and exact location unavailable.
Two indirect fatalities were reported by the Maricopa County Department of Public Health, with their details, such as age, gender, circumstances, and exact location unavailable.
Three fatalities (1 direct and 2 indirect) were reported by the Maricopa County Department of Public Health, with their details, such as age, gender, circumstances, and exact location unavailable.
As the offices recorded each death: direct deaths were caused by the weather itself, indirect ones by something it set in motion.
| Event | Date | Age | Sex | Where | Kind |
|---|---|---|---|---|---|
| Heat, Central Phoenix | 2021-07-01 | Unknown | Direct | ||
| Heat, Central Phoenix | 2021-07-01 | Unknown | Indirect | ||
| Heat, Central Phoenix | 2021-07-02 | Unknown | Indirect | ||
| Heat, Central Phoenix | 2021-07-02 | Unknown | Indirect | ||
| Heat, Central Phoenix | 2021-07-02 | Unknown | Indirect | ||
| Heat, Central Phoenix | 2021-07-03 | Unknown | Indirect | ||
| Heat, Central Phoenix | 2021-07-03 | Unknown | Indirect | ||
| Heat, Central Phoenix | 2021-07-03 | Unknown | Direct | ||
| Heat, Central Phoenix | 2021-07-03 | Unknown | Indirect | ||
| Heat, Central Phoenix | 2021-07-04 | Unknown | Indirect | ||
| Heat, Central Phoenix | 2021-07-04 | Unknown | Indirect | ||
| Heat, Central Phoenix | 2021-07-05 | Unknown | Direct | ||
| Heat, Central Phoenix | 2021-07-05 | Unknown | Indirect | ||
| Heat, Central Phoenix | 2021-07-05 | Unknown | Indirect |
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2021Every state in 2021This day in weather historyWarnings in Arizona, July 2021
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1066907, 1066908, 1066909, 1066910, 1066911.